What is the difficulty level of this kata?..

Sounds like you're not familiar with Haskell.

Available language features in Haskell make my solution there much more readable ( and short ) than in JS. My JS solution has so much overhead to implement necessary features I consider it pretty much unreadable, even if in essence it's pretty simple.

I've commented something earlier in the vein of this. At first I was too busy looking for an elegant solution and then gave in and submitted something rather simple but non-elegant. I believe the most elegant solution I've seen among the two languages I'm familiar with is JohanWiltink's JS solution.

Your comment reminds me of this. A very simple melody, but it took 1 genius to come up with it.

Very strange kata... At first, you want to implement smth serious, but afterwards a 8-7 level kyu algorithm beats the task. Nevertheless, it definitely was a great experience.

Amazing kata, one of my favourite ones from now on.) Thanks for the opportunity of thinking out of the box and to dig deeper on the matter of dp.

Amazing Kata, thanks for a something closely related to the real world problems.